This invention relates to folded sheet material, regardless of whether it is in a folded or unfolded condition.
It is known to fold maps with a first set of vertical concertina folds (which term means that the folds are alternately towards and away from the front of the sheet) and, once the map is so folded, to impose a second set of folds (not concertina) that are horizontal. It is further known for such a map to have a stiffening portion which extends over the whole of one corner segment produced by the folds and beyond this for a similar area outside the map so that when the map has been folded completely the outside stiffened portion can be folded over the map so that the map is wholly contained between the two parts of the stiffened portion that are hinged together.